Temperature-compensated indicating instrument



Patented July 18, 1939 UNITED STATES PATENTOFFICE- TEMPERATUBE-COMPENSATED INDICATIN G INSTRUMENT Anton Menzer, Brooklyn, N. Y.-, assignor to Bendix Aviation Corporationi South Bend, hit, a corporation of Delaware Application my 21, 1937, Serial No, 144,094

. 3 Claims. (01. 13-4)" The present invention relates to indicating inducing the outside static air pressure tothe instruments and more particularly to means for terior of the instrument casing. compensating the effect of temperature upon The operating mechanism is mounted on a an indicating instrument. frame of any suitable type, comprising casting 9 Instruments utilizing expansibleor resilient eleheld in place by spacer ring II which holds the ments as actuating means are subject to various frame against an annular abutment 50 formed in sources of error Upon a change in temperature, the casing, by pressing against dial ll abutting for instance, the modulus of elasticity of the the face of the casting 9. material used in the expanding or resilient ele- Mounted on base so in opening I! by means of ment changes, thereby causing error. rod l3 and screw H (see Fig. 2) are diaphragms Accordingly, one of the objects of the present is. Adjustably mounted in a post It extending i invention is to provide novel means in an indifrom the .top diaphragm, is a rod i! to which nated.

eating or measuring instrument, whereby the is pivoted one end ofa diaphragm link I! by pin foregoing undesirable characteristic is elimi- 19. Rod i'l maybe of bi-metal,if desired, in order to provide temperature compensation at 5 Another object is to provide in an indicating or theaero. indication of the altimeter. 'Screw 2| .measuring instrument novel means whereby fastens the l'l in place after it hasbeen changes in the modulus of elasticity of the actuproperly adiusted.- I

ating element'due to changes in temperature are The novel means of the invention are now compensated to eliminate errors in the instruprovided and. for. this purpose one end of the ment. rockshaft arm 22. is rotatably connected to the A further object is to provide novel means 'other end of link l l ,by pin 2| (see Fig. 3) while whereby themeans utilized to compensate for said arm passes freely through opening 23 in "changes .in the modulus of elasticity may be ad'- the rock shaft Zlfand is threaded at Ma whereby can be produced. 25 fastenedto the 'ro'clr'shaitby screw 26. In The above and further obiects and advantages accordance with the invention the arm flpasses oi the invention will appear more'f-ully hereinthrough ,an-openingfilin the bi-metal element after from' a consideration of the detailed de- 25 and is adjustably connected thereto by nuts iusted so that the most eifective compensation it is adiustably connected ton bi-metal element 25 3o scription which'follows, taken together with the 2! and I0. cooperating, with the threaded end 22a 3 accompanying drawing, wherein is illustrated one of the rock shaft arm 22." '1 embodiment of the invention. .It is to be ex- Bi-metal element 25 is constructed of two difpressly, understood, however, that the drawing ferentimetals in'a manner well-known in the is for the purpose of illustration and description art and is mounted parallel to the axis of rockonly and is not-designed as a definition of the shaft 24. Upon expansion and contraction of limits ofthe invention reference being had for the iii-metal element with changesin temperathis purpose to the appended claims. turegefleetive lever arm between thelink II V In the drawing wherein like reference char-" and the rockshaft 24 is varied. By changing the .acters refer to like parts throughout the several mm 0f Misha m 2! i the b m Fig.1 is aside elevation, partly in section, of screw threaded end no of the rockshaft arm, a device embodying the invention; I the initial setting of arm 22 may be adjusted. Fig. 2 is a section taken alon'g the line 3-2 ofv The novel means transmitthe motion of the Fig.1; and diaphra m: to the rockshaft 24 which is mounted Fig. 3 is a detailed view, partly in section, of a for rotation by an extension on one end thereof part of the devica 'showing the'msnner of mount-' iournaled at II (see Fig. 1) in the face of ing the bi-metal elementand rockshaft casting I andby a journal formed in the other Referring to the drawing wherein the invenend of said rockshaft cooperating with an extenelement II by means'ofnuts 29 and ill and the 40 tion is illustrated as applied to an altimeten'the sion 32 of an adjustable member 33 held in place a 50 "operating mechanism of the altimeter is shown in an opening 34 by screw 36. Mounted on the as enclosew in a casing I, said casing being rockshaft 24 at one end thereof and fastened closed by a cover glass .0 held in place by a rethereto is'the hair spring whose other end is silient ringfjfi Screw fitting 0 extending i'earfastened to the frame by clamping it in an openwardly of the casing provides means for introing in rod I! (see Ft. 2). This spring serves to itake up the backlash between the sector 88 and pinion 39.

The sector 38 is mounted for rotation with rockshaft 24 and meshes with pinion 38 integral with shaft 40 carrying pointer 4| at one end thereof moving over a scale on'dial I I. Shaft 48 isjournaled at one end in plate 42 mounted on the frame by spacers 43 and screws 44 and is journaled near the pointer end at 45.

With changes in, temperature the modulus of the link l8 and the rockshaft.

If the diaphragm is constructed of an ordinary metal having a negative temperature coefllcient of modulus of elasticity, upon a decrease of tem-' perature the amount of expansion of said diaphragm for a certain increment of pressure will be reduced from what it would be at a higher temperature. This reduction in expansion would be indicated by a reduced movement of the pointer.

In order to compensate for said reduction the bimetalelement is so designed and mounted that.

it moves away from the rockshaft with a decrease in temperature thereby reducing the effective lever arm between link I8 and said rockshaft. By the reduction of said lever arm the point of application of the force due to the expanding diaphragm travels in a circular path of smaller radius whose center is the center of the rockshaft. A smaller expansion of the diaphragm, therefore, is changed to an increased angular rotation of rockshaft 24 and such increased angular rotation is transmitted tothe pointer thereby oilsetting the reduced movement of the pointer due to the lesser expansion of the diaphragm at said lower temperature.

The mounting of the bi-metal element 25 parallel to the rockshaft and the adjustable connection of rockshaft arm 22 at right angles thereto provide a mechanism whereby the initial lever arm between the link and the bi.metal element can be accurately adjusted thereby enabling the ad ustment of said lever arm so that the most eifective compensation can be produced without injury to the bi-metal element or any impairment of the functions thereof.

The operation'is as follows: When the diaphragms expand, due, for instance, to a decrease in pressure on the outside thereof, diaphragm link 18 is moved upwardlyto actuate the rockshaft arm 22 to thereby rotate rockshai't 24. The eil'ective lever arm between link l8 and the rock- -shaft is varied by movement of bi-metal element 25 with temperature changes thereby ofl'setting changes in the expansion in the diaphragms due to changes of temperature affecting the modulus of elasticity.

1 The movement transmitted to the rockshait 24 rotates the gear sector 88 thereby rotating pinion 38 and shaft 48 to rotate the pointer 4|. Spring 36 serves to take up any backlash between sector 88 and pinion 39.

Means are therefore provided whereby errors due to temperature are compensated and the most efli'cient setting for proper compensation can beaccurately determined and set.

Although but one embodiment has been illustrated and described, further changes and modifications' in form, materials and relative arrangements of parts, which will now appear to those skilled inthe-art, may be made without departing from-the scope of the invention. Reference, therefore,-is to be had to the appended claims for a definition of the limits of the invention.

' What is claimed is:

i. In a device of the character described, a rockshaft a bi-metal element spaced. parallel to said rockshaft and attached thereto at one end of said element, an opening in said rockshaft, an opening in said element, and an arm passing through said openings and adjustably attached to the other-end of said element whereby said arm may-be freely moved through the opening in said rockshaft by the movement of said element withchanges in temperature.

2. In a device of the character described a movable diaphragm, means mounted for rotation by the motion of said diaphragm, a bimetal element connected to -said first means at vone end thereof, means connecting'the other end of said element to said diaphragm, one end of said connecting means having a threaded portion passing through said element, and means for locking said connecting means to said element at adjustable positions along said threaded portion.

3. In a device of the character described, an aneroid, a rockshaft, a bi-metal element, means mounting said bi-metal element on said rockshaft and parallel thereto, means connecting said aneroid and said bi-metal element including an.

arm, and means whereby said arm may be connected to said element at various points along the length of said arm. ANTON 

